Biomedical subjects

A P Batista

Publications and source records attributed to A P Batista.

10 recordsLinked to original sources

PubMed2003

Properties of spike train spectra in two parietal reach areas.

In the lateral intraparietal area (LIP), a saccade-related region of the posterior parietal cortex (PPC), spiking activity recorded during the memory period of an instructed-delay task exhibits temporal structure that is spatially tuned. These results provide evidence for the existence of 'dynamic memory fields' which can be read-out by other brain areas, along with information contained in the mean firing rate, to give the direction of a planned movement. We looked for evidence of dynamic memory fields in spiking activity in two parietal reach areas, the parietal reach region (PRR) and area 5. Monkeys made center-out reaches to eight target locations in an instructed-delay task with a memory component. Neurons in both areas exhibited sustained activity during the delay period that was spatially tuned. Many single cell PRR spectra exhibited spatially tuned temporal structure, as evidenced by a significant and spatially tuned peak in the 20-50 Hz band. The PRR population spectrum of spike trains was also tuned, with the peak power centered on approximately 25 Hz. In contrast, area 5 spiking activity did not exhibit any significant temporal structure. These results suggest that different mechanisms underlie sustained delay period activity in these two areas and that dynamic memory fields, as revealed by our techniques, are more prominent in PRR than in area 5. Temporal structure in the spike train and local field potential (LFP) are related in at least one other brain area (LIP). The present results suggest then that LFP activity obtained from PRR may be better suited than area 5 LFP activity for use in neural prosthetic systems that incorporate analysis of temporal structure as part of a decode mechanism for extracting intended movement goals.

Action Potentials↗

PubMed2001

The parietal reach region codes the next planned movement in a sequential reach task.

Distinct subregions of the posterior parietal cortex contribute to planning different movements. The parietal reach region (PRR) is active during the delay period of a memory-guided reach task but generally not active during a memory-guided saccade task. We explored whether the reach planning activity in PRR is related to remembering targets for reaches or if it is related to specifying the reach that the monkey is about to perform. Monkeys were required to remember two target locations and then reach to them in sequence. Before the movements were executed, PRR neurons predominantly represented the reach about to be performed and only rarely represented the remembered target for the second reach. This indicates the area plays a role in specifying the target for the impending reach and may not contribute to storing the memory of subsequent reach targets.

Animals↗

PubMed2000

Visuo-motor control: giving the brain a hand.

Sensory information is acquired in spatial coordinate systems linked to sense organs, yet movement must be executed in coordinate systems linked to motor effector organs. Neurophysiological experiments are yielding new insights into how the brain transforms coordinate systems to facilitate movement.

Animals↗

PubMed2000

Intention-related activity in the posterior parietal cortex: a review.

Over the last few years it is becoming increasingly apparent that an important role of the posterior parietal cortex is to process sensory information for the purpose of planning actions. We review studies showing that a large component of neural activity in area LIP is related to planning saccades and activity in a nearby parietal reach region (PRR) to reaches. This intention related activity dominates the delay period in delayed movement tasks, and also comprises a substantial component of the transient response. These findings, along with additional anatomical and physiological evidence, lends support to the idea that different cortical areas within the PPC represent plans for different actions. We also found strong modulation of activity when movement plans were changed without changes in the locus of attention. This result suggests that PPC, which has been postulated to play a role in shifting attention, may also play a role in changing movement intentions. Sensory related activity was also present in these tasks and may be related to the stimulus or to attention. These experiments show that there are intention and sensory related activities in the PPC consistent with its proposed role in sensory-motor transformations. These studies also show that care must be taken to measure intention-related signals and not assume that all task dependent modulation in the PPC reflects attention.

Movement↗

PubMed2000

Saccade-related activity in the parietal reach region.

In previous experiments, we showed that cells in the parietal reach region (PRR) in monkey posterior parietal cortex code intended reaching movements in an eye-centered frame of reference. These cells are more active when an arm compared with an eye movement is being planned. Despite this clear preference for arm movements, we now report that PRR neurons also fire around the time of a saccade. Of 206 cells tested, 29% had perisaccadic activity in a delayed-saccade task. Two findings indicate that saccade-related activity does not reflect saccade planning or execution. First, activity is often peri- or postsaccadic but seldom presaccadic. Second, cells with saccade-related activity were no more likely to show strong saccadic delay period activity than cells without saccade-related activity. These findings indicate that PRR cells do not take part in saccade planning. Instead, the saccade-related activity in PRR may reflect cross-coupling between reach and saccade pathways that may be used to facilitate eye-hand coordination. Alternatively, saccade-related activity may reflect eye position information that could be used to maintain an eye-centered representation of intended reach targets across eye movements.

Animals↗

PubMed1999

Reach plans in eye-centered coordinates.

The neural events associated with visually guided reaching begin with an image on the retina and end with impulses to the muscles. In between, a reaching plan is formed. This plan could be in the coordinates of the arm, specifying the direction and amplitude of the movement, or it could be in the coordinates of the eye because visual information is initially gathered in this reference frame. In a reach-planning area of the posterior parietal cortex, neural activity was found to be more consistent with an eye-centered than an arm-centered coding of reach targets. Coding of arm movements in an eye-centered reference frame is advantageous because obstacles that affect planning as well as errors in reaching are registered in this reference frame. Also, eye movements are planned in eye coordinates, and the use of similar coordinates for reaching may facilitate hand-eye coordination.

Animals↗

PubMed1998

Posterior parietal areas specialized for eye movements (LIP) and reach (PRR) using a common coordinate frame.

The posterior parietal cortex (PPC) has long been considered a sensory area specialized for spatial awareness and the directing of attention. However, a new, far reaching concept is now emerging that this area is involved in integrating sensory information for the purpose of planning action. Moreover, experiments by our group and others over the last two decades indicate that PPC is in fact anatomically organized with respect to action. PPC also is an 'association' cortex which must combine different sensory modalities which are coded in different coordinate frames. We have found, at least for two different cortical areas within PPC, that different sensory signals are brought into a common coordinate frame. This coordinate frame codes locations with respect to the eye, but also gain modulates the activity by eye and body position signals. An interesting feature of this coordinate representation at the population level is that it codes concurrently target locations in multiple coordinate frames (eye, head, body and world). Depending on how this population of neurons is sampled, different coordinate transformations can be accomplished by the same population of neurons.

Animals↗

PubMed1998

Change in motor plan, without a change in the spatial locus of attention, modulates activity in posterior parietal cortex.

The lateral intraparietal area (LIP) of macaque monkey, and a parietal reach region (PRR) medial and posterior to LIP, code the intention to make visually guided eye and arm movements, respectively. We studied the effect of changing the motor plan, without changing the locus of attention, on single neurons in these two areas. A central target was fixated while one or two sequential flashes occurred in the periphery. The first appeared either within the response field of the neuron being recorded or else on the opposite side of the fixation point. Animals planned a saccade (red flash) or reach (green flash) to the flash location. In some trials, a second flash 750 ms later could change the motor plan but never shifted attention: second flashes always occurred at the same location as the preceding first flash. Responses in LIP were larger when a saccade was instructed (n = 20 cells), whereas responses in PRR were larger when a reach was instructed (n = 17). This motor preference was observed for both first flashes and second flashes. In addition, the response to a second flash depended on whether it affirmed or countermanded the first flash; second flash responses were diminished only in the former case. Control experiments indicated that this differential effect was not due to stimulus novelty. These findings support a role for posterior parietal cortex in coding specific motor intention and are consistent with a possible role in the nonspatial shifting of motor intention.

Animals↗

PubMed1997

Coding of intention in the posterior parietal cortex.

To look at or reach for what we see, spatial information from the visual system must be transformed into a motor plan. The posterior parietal cortex (PPC) is well placed to perform this function, because it lies between visual areas, which encode spatial information, and motor cortical areas. The PPC contains several subdivisions, which are generally conceived as high-order sensory areas. Neurons in area 7a and the lateral intraparietal area fire before and during visually guided saccades. Other neurons in areas 7a and 5 are active before and during visually guided arm movements. These areas are also active during memory tasks in which the animal remembers the location of a target for hundreds of milliseconds before making an eye or arm movement. Such activity could reflect either visual attention or the intention to make movements. This question is difficult to resolve, because even if the animal maintains fixation while directing attention to a peripheral location, the observed neuronal activity could reflect movements that are planned but not executed. To address this, we recorded from the PPC while monkeys planned either reaches or saccades to a single remembered location. We now report that, for most neurons, activity before the movement depended on the type of movement being planned. We conclude that PPC contains signals related to what the animal intends to do.

Animals↗

PubMedDate not supplied

Familial camptodactyly.

Camptodactyly is a permanent flexion deformity at the interphalangeal joints, usually at the proximal, interphalangeal joints. It is by far most commonly encountered in the little finger, but it can occur in any of the others, and may be associated with a deformity in the little finger or not. It is usually bilateral. It can also appear in the toes, the second toe being the most frequently affected. This deformity can appear in two different situations: it can occur in isolation, or can be a part of a malformative syndrome. It can also be sporadic or be transmitted as an autosomal dominant trait [1, 5, 7, 8]. We report a case of familial camptodactyly not associated with any other disorders: the differential diagnoses included scleroderma and Dupuytren's contracture.

Child↗